In UMTS (Universal Mobile Telecommunications System) networks, for the purpose of improving spectral efficiency and further improving data rates, by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access), it is performed exploiting maximum features of the system based on W-CDMA (Wideband Code Division Multiple Access). For the UMTS network, for the purpose of further increasing high-speed data rates, providing low delay and the like, Long Term Evolution (LTE) has been studied (for example, see Non-patent Document 1).
In the 3G system, a fixed band of 5 MHz is substantially used, and it is possible to achieve transmission rates of approximately maximum 2 Mbps in downlink. Meanwhile, in the LTE-scheme system, using variable bands ranging from 1.4 MHz to 20 MHz, it is possible to achieve transmission rates of maximum 300 Mbps in downlink and about 75 Mbps in uplink. Further, in the UMTS network, for the purpose of further increasing the wide-band and high speed, successor systems to LTE have been studied (for example, LTE Advanced (LTE-A)). For example, in. LTE-A, it is scheduled to increase 20 MHz that is the maximum system band in LTE specifications to about 100 MHz.
In the LTE-scheme system (LTE system), a base station apparatus measures uplink channel quality based on an SRS (Sounding Reference Signal) for channel quality measurement transmitted from a mobile station apparatus, performs scheduling for the mobile station apparatus to transmit a data channel signal (PUSCH: Physical Uplink Shared Channel), and issues instructions on a PDCCH (Physical Downlink Control Channel). In this case, the SRS for channel quality measurement is multiplexed into a last symbol in some of subframes constituting a radio frame in uplink, and is transmitted periodically at intervals of 5 msec from the mobile station apparatus to the base station apparatus.